Given statements $A$ and $B$, are the formulae $(\lnot A) \land (\lnot B)$ and $(\lnot A) \lor (\lnot B)$ equivalent?
One way of verifying whether two boolean expressions are equivalent is to assign all possibilities to all variables, and comparing all results.




A
B
f1
f2




T
T
F
F


T
F
F
T


F
T
F
T


F
F
T
T




We can see (F, F, F, T) does not equal (F, T, T, T), for example for the assignment (A, B) = (T, F) we get result (f1, f2) = (F, T) , meaning f1 != f2.